The present invention relates to a conventional incandescent light bulb having at least two filaments enclosed in an evacuated glass bulb which is connected to an electric current to make them glow. The first filament is an incandescent type that is aligned parallel to a second filament that is equipped with a solar-photovoltaic array that collects the light energy that is being emitted and wasted from the first incandescent filament. One of the filaments is operated by ordinary 110V or 220 alternating current while the other is operated by current from a battery. The battery is charged by the photovoltaic array which converts a portion of the light emitted by the light bulb back into electrical energy, thereby increasing the light bulb's efficiency and lowering the operating cost.
On Jan. 27, 1880 Thomas Alva Edison was granted U.S. Pat. No. 223,898 on an electric lamp. Prior to Edison's invention, light by incandescence had been obtained from low resistance carbon rods placed in closed vessels in which the air had been replaced by other gases. Edison's invention consisted of carbon wire or sheets placed in a vacuum which protected against oxidation and injury to the filament. That, in Edison's day, was a radical departure from prior attempts at a commercially feasible electric lamp. The present invention represents yet a further improvement to the ubiquitous light bulb.
Dual-filament incandescent light bulbs are well-known in the prior art as a means of increasing the effective life of an incandescent bulb. These devices employ filament switching devices which upon failure of the primary filament, switches power to a secondary filament. Most of these devices use a fusible conductor which restrains a leaf-spring contact. When the primary filament fails, the surge of current which occurs due to the failing filament ruptures the fusible conductor. The rupture of the fusible conductor releases the leaf-spring contact which then causes power to be routed to the secondary filament rather than the primary filament.
Other devices have improved on the basic concept by designing switching devices which fit within a screw base the size of a conventional light bulb as disclosed by U.S. Pat. No. 4,580,079. None of these devices, however, by simply increasing the effective life of a single incandescent bulb, achieve any energy savings. That is, their sole utility is to be found in the convenience afforded to users of not having to change light bulbs as often as with single filament bulbs.
It is an object of the present invention, therefore, to provide a dual filament incandescent bulb which not only lasts longer than conventional single-filament bulb, but requires less power to operate over the life of the bulb. The present invention utilizes the fact that, in most applications, users of conventional incandescent bulbs find the bulbs to be too bright. Users of these bulbs therefore employ means such as lampshades which serve to block some of the light emitted by the light bulb in order to achieve the desired ambient lighting condition. Some consumers find, however, that even lampshades are inadequate to achieve the desired dimming of the emitted light. The light bulb industry has responded therefore, by producing light bulbs wherein the bulb is coated with a light absorbing substance enabling a dimmer or "softer" light to be emitted. These types of bulbs have been widely accepted by the public.
The means of blocking light emitted by incandescent bulbs described above, whether they be lampshades or coated bulbs, all result in a good portion of the light emitted by the bulb being wasted. This also means, of course, that the corresponding electrical energy which produced the light is wasted also. One reason that consumers have not simply resorted to lower wattage bulbs to achieve the desired reduction in emitted light is that a certain light level is desired which can reflect off of room surfaces. That is, when a lampshade is employed to block some of the light emitted by an incandescent bulb, the consumer still desires the light emitted through the top and bottom of the lampshade to be unattenuated. The unattenuated light may then reflect off of room surfaces to produce the desired ambient lighting condition. Similarly, in the case of coated light bulbs, the coating absorbs only certain frequencies of the light emitted by the filament, leaving others unattenuated. Consumers evidently desire only certain frequencies of the light emitted by the light bulb to attenuated. Since no incandescent filaments can be made which produce light having either the desired directional intensity variation or frequency characteristics desired by most consumers, light blocking devices are the only means available which enable incandescent bulbs to produce light having the characteristics desired by consumers for room lighting.
An object f the present invention is to provide an improved version of the original incandescent bulb invented by Thomas Alva Edison. It is an object of the present invention, therefore, to provide a means for lighting rooms in a manner acceptable to consumers with or without the concomitant use of an ordinary lampshade. It is a further object of the present invention to lessen the waste of electrical energy which occurs when the light emitted by an incandescent filament is partially blocked to achieve a desired lighting condition. A still further object of the present invention is to provide a means for extending the effective life of an incandescent filament.